Browse Prior Art Database

E-Beam Mask Writing at High Exposure Doses

IP.com Disclosure Number: IPCOM000049564D
Original Publication Date: 1982-Jun-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Giuffre, GJ: AUTHOR [+2]

Abstract

An interposing layer of resist between the E-beam resist and substrate is employed as a thermal barrier to prevent heat from the substrate, generated by electrons absorbed during exposure, from affecting the sensitivity of the upper resist layer.

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E-Beam Mask Writing at High Exposure Doses

An interposing layer of resist between the E-beam resist and substrate is employed as a thermal barrier to prevent heat from the substrate, generated by electrons absorbed during exposure, from affecting the sensitivity of the upper resist layer.

Resist materials currently used by E-beam exposure tools in the manufacture of masks and reticles for photolithography require high exposure doses (greater than or equal to 5Muc/cm/2/) to produce developed positive relief images of high fidelity. At these doses, however, the images of adjacent pattern elements (rectangles), which are successively exposed, show a gross deterioration in comparison to others. Shape control is lost due to "blooming" of the images in a way that depends on the history of the exposure.

This problem affects patterns exposed on masks, but not those exposed on wafers, due to the poor thermal conductivity of the mask substrates (typically glass) as compared to wafers (silicon). The energy of the beam electrons absorbed in the glass gives rise to local heat accumulations, within the time required to expose several adjacent rectangles. The resulting temperature increase leads to a local increase in the resist sensitivity, such that at nominal beam intensity the dose is effectively excessive, causing the blooming.

As shown in the figure, the blooming may be minimized by coating chrome mask material 1 with two layers of resist 3 and 5, each having different characteristics. The interposing layer 3 acts as a thermal barrier to prevent heat from glass su...